Carbidopa

• Some studies have found that the combination of 5-HTP and carbidopa 5-HTP and carbidopa may have a beneficial effect in the treatment of intention myoclonus, a neuromuscular disorder. Other research has not been able to confirm these outcomes.
• Growdon JH, et al. Neurology 1976;26:1135-1140;
• Van Woert MH, et al. N Engl J Med 1977;296:70-75;
• Magnussen I, et al. Acta Neurol Scand 1978;57:289-294;
• Magnussen I, et al. Acta Pharmacol Toxicol (Copenh). 1981 Sep;49(3):184-189;
• Magnussen I, Van Woert MH. Eur J Clin Pharmacol. 1982;23(1):81-86;
• Van Woert MH. Prog Clin Biol Res. 1983;127:43-52
• Sternberg et al reported a scleroderma-like illness which developed in a patient treated with L-5 hydroxytryptophan (L-5HTP) and carbidopa for intention myoclonus. The patient had high plasma kynurenine levels that remained high when the L-5HTP-carbidopa combination was discontinued and rose again when the drug was reintroduced, suggesting that the drug unmasked an abnormality in one of the enzymes that catabolize kynurenine. They concluded that high plasma serotonin and the abnormality associated with elevated kynurenine were important in the pathogenesis of some scleroderma-like illnesses. Other researchers have published similar reports.Until further research is conducted into the interactions of carbidopa and 5-HTP individuals taking carbidopa should refrain from taking 5-HTP as a supplement unless they have consulted with and are under the supervision of a physician trained in nutritional therapies.
• Sternberg EM, et al. N Engl J Med 1980 Oct 2;303(14):782-787
• Auffranc JC, et al. Ann Dermatol Verereol 1985;112:691-692
• Joly P, et al. J Am Acad Dermatol 1991;25:332-333.
• Iron supplements taken with carbidopa interfere with the action of the drug. Individuals using carbidopa should not take iron supplements without consulting with the prescribing physician and/or their pharmacist.
• Campbell NR, Hasinoff BB. Brit J Clin Pharmacol 1991;31:251-255; Campbell NR, et al. Br J Clin Pharmacol 1990 Oct;30(4):599-605
• Pharmaceutical MAOI's are usually discontinued 2-4 weeks before starting Sinemet (levodopa-carbidopa) usage. Since it is has been proposed that Hypericum acts in a manner similar to MAO-inhibitors, similar caution would be advised with regard to a potential interaction pending more conclusive research findings.